INTRODUCTION

Roads, and the logging often associated with them, have a wide range of profound impacts on forest ecosystems. These include direct and indirect effects on individual plant and animal species, as well as broad changes in ecosystem structure and function. Though much remains to be investigated about the full nature and scope of these impacts, a large body of existing scientific literature evaluates their severity, extent, and timescale.

This annotated bibliography provides an overview of primary research, almost all from peer-reviewed journals, documenting the adverse impacts of roads and logging on North American forest ecosystems. The research included focuses on effects that extend beyond the immediate road and its edges. Such impacts compromise the diversity and health of entire landscapes and their species as well as that of the road environs themselves. Literature clarifying the ecological significance of impacts is also reviewed.

Six categories of impact are addressed here, each in its own chapter. These include effects on sensitive wildlife species from displacement, dispersal barriers, road kill, and reduced reproductive success. Also covered is the spread of tree diseases by road construction, tree stumps, and logging wounds. Overlapping with disease problems is the increase in pest infestations at forest edges, in logging debris, and in diseased trees. Fourth, the dispersal of non-native plant and animal species along roads and disturbed habitat is reviewed. A fifth category is damage to soils by logging and road-building equipment. Sixth, the bibliography reviews literature about road- and logging-related degradation of stream ecosystems. A seventh and final chapter summarizes relevant literature reviews, each of which itself discusses numerous studies; it also covers a few studies that attempt to quantify how much of the forest landscape is affected by certain road impacts.

Within these seven chapters, each annotation begins with one or more "Key Findings," identifying the central significance of a published work (these Key Findings are also listed in the Summary following this Introduction). A synopsis of the article follows, providing a brief account of the study’s methodology, geographical location, and pertinent results.

The body of work investigating how forest management affects wildlife is particularly extensive. Chapter One in this report (Harm to Wildlife) focuses on a subset of this research – that showing the direct impacts of management on sensitive wildlife. It includes studies documenting changes in behavior, reduced reproduction rates, increased mortality, and changes in community composition and diversity. Generally, however, this report does not attempt to review the voluminous literature about habitat associations for individual species. From much of this latter work, good inferences can be drawn concerning the adverse wildlife impacts of road building and, even more, of logging.

Also not included are studies that show the significant threat roads pose by providing poachers access into pristine areas. Many large mammals, such as grizzly bears, black bears, and elk, suffer from increased hunting pressure near roads and may not be able to maintain their populations near roadsides.

Finally, the impact of roads or logging on forest fire hazard is an important issue that has not been addressed in this bibliography. Increased ignition frequency along roads has been well established. In addition, some published studies indicate that logging can increase fire hazard, perhaps because of slash left behind, drier forest conditions under open canopies, damage to residual trees, compromised soil resources, or disrupted ground water regimes. This is a complex topic that deserves separate consideration in its own right.